Migrate UI to COSS components + COSS neutral theme; add i18next

Components:
- Replace components/ui primitives with COSS equivalents from the @coss/* shadcn
  registry. Add menu/preview-card/group; remove the superseded dropdown-menu,
  hover-card, button-group; keep carousel (no COSS equivalent).
- Migrate live call sites to canonical COSS APIs preserving layout/behavior:
  sidebar menus (nav-user, team-switcher, nav-notifications), chat-input radio
  menu, patient dialogs/cards, auth forms (FieldGroup -> flex column), settings.
- ai-elements: migrate the live conversation/message with behavior parity
  (Tooltip via render, Group/GroupText); repoint dormant files (hover-card ->
  preview-card, dropdown-menu -> menu, button-group -> group, InputGroupButton
  -> Button). Residual pre-existing Base UI type drift stays behind
  ignoreBuildErrors.

Theme:
- Adopt COSS default neutral tokens in globals.css with light + dark palettes.
- Add next-themes (defaultTheme=dark, enableSystem) and drop the forced dark
  class. Align font variables to the COSS contract (--font-sans/-heading/-mono).
  Make scrollbars theme-aware.

i18n:
- Add i18next + react-i18next (lib/i18n/config.ts, locales/en/translation.json,
  components/i18n-provider.tsx mounted in layout). Convert auth forms, sidebar
  nav, and settings tabs to useTranslation() as the reference pattern.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/components/ui/tooltip.tsx

@@ -1,66 +1,67 @@
-"use client"
+"use client";
 
-import { Tooltip as TooltipPrimitive } from "@base-ui/react/tooltip"
+import { Tooltip as TooltipPrimitive } from "@base-ui/react/tooltip";
+import type React from "react";
+import { cn } from "@/lib/utils";
 
-import { cn } from "@/lib/utils"
+export const TooltipCreateHandle: typeof TooltipPrimitive.createHandle =
+  TooltipPrimitive.createHandle;
 
-function TooltipProvider({
-  delay = 0,
-  ...props
-}: TooltipPrimitive.Provider.Props) {
-  return (
-    <TooltipPrimitive.Provider
-      data-slot="tooltip-provider"
-      delay={delay}
-      {...props}
-    />
-  )
+export const TooltipProvider: typeof TooltipPrimitive.Provider =
+  TooltipPrimitive.Provider;
+
+export const Tooltip: typeof TooltipPrimitive.Root = TooltipPrimitive.Root;
+
+export function TooltipTrigger(
+  props: TooltipPrimitive.Trigger.Props,
+): React.ReactElement {
+  return <TooltipPrimitive.Trigger data-slot="tooltip-trigger" {...props} />;
 }
 
-function Tooltip({ ...props }: TooltipPrimitive.Root.Props) {
-  return <TooltipPrimitive.Root data-slot="tooltip" {...props} />
-}
-
-function TooltipTrigger({ ...props }: TooltipPrimitive.Trigger.Props) {
-  return <TooltipPrimitive.Trigger data-slot="tooltip-trigger" {...props} />
-}
-
-function TooltipContent({
+export function TooltipPopup({
   className,
-  side = "top",
-  sideOffset = 4,
   align = "center",
-  alignOffset = 0,
+  sideOffset = 4,
+  side = "top",
+  anchor,
   children,
+  portalProps,
   ...props
-}: TooltipPrimitive.Popup.Props &
-  Pick<
-    TooltipPrimitive.Positioner.Props,
-    "align" | "alignOffset" | "side" | "sideOffset"
-  >) {
+}: TooltipPrimitive.Popup.Props & {
+  align?: TooltipPrimitive.Positioner.Props["align"];
+  side?: TooltipPrimitive.Positioner.Props["side"];
+  sideOffset?: TooltipPrimitive.Positioner.Props["sideOffset"];
+  anchor?: TooltipPrimitive.Positioner.Props["anchor"];
+  portalProps?: TooltipPrimitive.Portal.Props;
+}): React.ReactElement {
   return (
-    <TooltipPrimitive.Portal>
+    <TooltipPrimitive.Portal {...portalProps}>
       <TooltipPrimitive.Positioner
         align={align}
-        alignOffset={alignOffset}
+        anchor={anchor}
+        className="z-50 h-(--positioner-height) w-(--positioner-width) max-w-(--available-width) transition-[top,left,right,bottom,transform] data-instant:transition-none"
+        data-slot="tooltip-positioner"
         side={side}
         sideOffset={sideOffset}
-        className="isolate z-50"
       >
         <TooltipPrimitive.Popup
-          data-slot="tooltip-content"
           className={cn(
-            "z-50 inline-flex w-fit max-w-xs origin-(--transform-origin) items-center gap-1.5 rounded-xl bg-foreground px-3 py-1.5 text-xs text-background has-data-[slot=kbd]:pr-1.5 data-[side=bottom]:slide-in-from-top-2 data-[side=inline-end]:slide-in-from-left-2 data-[side=inline-start]:slide-in-from-right-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2 **:data-[slot=kbd]:relative **:data-[slot=kbd]:isolate **:data-[slot=kbd]:z-50 **:data-[slot=kbd]:rounded-lg data-[state=delayed-open]:animate-in data-[state=delayed-open]:fade-in-0 data-[state=delayed-open]:zoom-in-95 data-open:animate-in data-open:fade-in-0 data-open:zoom-in-95 data-closed:animate-out data-closed:fade-out-0 data-closed:zoom-out-95",
-            className
+            "relative flex h-(--popup-height,auto) w-(--popup-width,auto) origin-(--transform-origin) text-balance rounded-md border bg-popover not-dark:bg-clip-padding text-popover-foreground text-xs shadow-md/5 transition-[width,height,scale,opacity] before:pointer-events-none before:absolute before:inset-0 before:rounded-[calc(var(--radius-md)-1px)] before:shadow-[0_1px_--theme(--color-black/4%)] data-ending-style:scale-98 data-starting-style:scale-98 data-ending-style:opacity-0 data-starting-style:opacity-0 data-instant:duration-0 dark:before:shadow-[0_-1px_--theme(--color-white/6%)]",
+            className,
           )}
+          data-slot="tooltip-popup"
           {...props}
         >
-          {children}
-          <TooltipPrimitive.Arrow className="z-50 size-2.5 translate-y-[calc(-50%-2px)] rotate-45 rounded-[2px] bg-foreground fill-foreground data-[side=bottom]:top-1 data-[side=inline-end]:top-1/2! data-[side=inline-end]:-left-1 data-[side=inline-end]:translate-x-[1.5px] data-[side=inline-end]:-translate-y-1/2 data-[side=inline-start]:top-1/2! data-[side=inline-start]:-right-1 data-[side=inline-start]:translate-x-[-1.5px] data-[side=inline-start]:-translate-y-1/2 data-[side=left]:top-1/2! data-[side=left]:-right-1 data-[side=left]:translate-x-[-1.5px] data-[side=left]:-translate-y-1/2 data-[side=right]:top-1/2! data-[side=right]:-left-1 data-[side=right]:translate-x-[1.5px] data-[side=right]:-translate-y-1/2 data-[side=top]:-bottom-2.5" />
+          <TooltipPrimitive.Viewport
+            className="relative size-full overflow-clip px-(--viewport-inline-padding) py-1 [--viewport-inline-padding:--spacing(2)] data-instant:transition-none **:data-current:data-ending-style:opacity-0 **:data-current:data-starting-style:opacity-0 **:data-previous:data-ending-style:opacity-0 **:data-previous:data-starting-style:opacity-0 **:data-current:w-[calc(var(--popup-width)-2*var(--viewport-inline-padding)-2px)] **:data-previous:w-[calc(var(--popup-width)-2*var(--viewport-inline-padding)-2px)] **:data-previous:truncate **:data-current:opacity-100 **:data-previous:opacity-100 **:data-current:transition-opacity **:data-previous:transition-opacity"
+            data-slot="tooltip-viewport"
+          >
+            {children}
+          </TooltipPrimitive.Viewport>
         </TooltipPrimitive.Popup>
       </TooltipPrimitive.Positioner>
     </TooltipPrimitive.Portal>
-  )
+  );
 }
 
-export { Tooltip, TooltipTrigger, TooltipContent, TooltipProvider }
+export { TooltipPrimitive, TooltipPopup as TooltipContent };